Lung function and six-minute walk test performance in individuals with sickle cell disease

BACKGROUND: Sickle Cell Disease (SCD), which is characterized by a mutation in the gene encoding beta hemoglobin, causes bodily dysfunctions such as impaired pulmonary function and reduced functional capacity. OBJECTIVE: To assess changes in pulmonary function and functional capacity in patients with SCD and to identify the relationships between these variables. METHOD: We evaluated sociodemographic, anthropometric, lung function (spirometry), respiratory (manovacuometer), peripheral muscle strength (Handgrip strength - HS) and functional capacity (i.e., the six-minute walk test) parameters in 21 individuals with SCD (average age of 29±6 years). Shapiro-Wilk, paired Student's, Wilcoxon, Pearson and Spearman correlation tests were used for statistical analyses, and the significance threshold was set at p<0.05. RESULTS: A total of 47.6% of the study subjects exhibited an altered ventilation pattern, 42.8% had a restrictive ventilatory pattern (RVP) and 4.8% exhibited a mixed ventilatory pattern (MVP). The observed maximal inspiratory pressure (MIP) values were below the predicted values for women (64 cmH(2)O), and the maximum expiratory pressure (MEP) values, HS values and distance walked during the 6MWT were below the predicted values for both men (103 cmH(2)O, 39 Kgf and 447 m, respectively) and women (64 cmH(2)O; 27 Kgf; 405 m, respectively). Positive correlations were observed between maximum voluntary ventilation (MVV) and MEP (r=0.4; p=0.046); MVV and BMI (r=0.6; p=0.003); and between HS and MIP (r=0.7; p=0.001), MEP (r=0.6; p=0.002), MVV (r=0.5; p=0.015), distance walked in the 6MWT (r=0.4; p=0.038) and BMI (r=0.6; p=0.004). CONCLUSIONS: SCD promoted changes in lung function and functional capacity, including RVPs and a reduction in the distance walked in the 6MWT when compared to the predictions. In addition, significant correlations between the variables were observed.